Aim: Comparison of peribulbar anaesthesia with sub-Tenon's anaesthesia in manual small incision cataract surgery in relation to time of onset of akinesia of extra ocular movements, pain at the time of administration, end of surgery and 1 hour after surgery and complications. Methodology: A randomized comparative study of 113 patients of which 57 patients received peribulbar anaesthesia and 56 patients received Sub-Tenon's anaesthesia. Results: The average time of onset of akinesia with sub-Tenon's anaesthesia was 2.78 ± 0.958minutes and peribulbar anaesthesia was 9.96 ± 2.141minutes. The difference was statistically significant (p = 0.00).Extraocular movements and ease of procedure between the two groups was almost the same and not statistically significant. Incidence of minor complications like chemosis and sub conjunctival haemorrhage were more in sub-Tenon's technique. Peribulbar anaesthesia ranked higher on pain score (5.12 ± 1.255) at the time of administration compared to Sub Tenon's anaesthesia (3.77 ± 1.716), the difference being statistically significant (p = 0.00). Conclusion: Sub-Tenon's anaesthesia is a safe and effective substitute for preibulbar anaesthesia in intraocular surgeries.

Cataract is the leading cause of preventable blindness in the world whereas cataract extraction with intraocular lens implantation is perhaps the most effective surgical procedure in all of medicine.[1] Cataract surgery constitutes by far the most common surgical procedure performed under local anesthesia. Hence, therefore, it is a need to make the anesthesia safe technique safe, effective, and economically feasible, especially in India.

Retrobulbar anesthesia was previously commonly used for cataract extraction. It was gradually replaced by peribulbar anesthesia because of the serious needle-related complications associated with the former such as retrobulbar hemorrhage, optic nerve damage, and globe perforation.[2]

In this context, sub-Tenon's anesthesia is gaining popularity providing a quicker onset of anesthesia, better analgesia, more consistency and effectiveness and better patient compliance, and faster patient rehabilitation.[3] Also as the needle used is blunt, it is thought to completely avoid the vascular and optic nerve injuries and provide better anesthesia without the drawbacks of topical anesthesia.

Materials and Methods

This comparative study was done on 113 patients who were undergoing manual small incision cataract surgery. They were randomized into two groups, Group 1 peribulbar anesthesia and Group 2 sub-Tenon's anesthesia. These studies had Institutional Ethics approved and strictly adhered to the principles of the Declaration of Helsinki. This study was conducted in a tertiary hospital from September 2015 to April 2017 in the Department of Ophthalmology. A complete ophthalmic examination including best corrected visual acuity, dilated fundus evaluation was done for all patients. All the patients undergoing cataract surgery after obtaining general medicine clearance were included in the study. Patients below the age of 40 years, traumatic/complicated cataract, previous ocular surgeries, and allergic to xylocaine were excluded from the study. For peribulbar anesthesis, the eye was painted with 10% povidone-iodine solution and draped. Lid speculum was placed. 7 ml of anesthetic mixture was prepared with 4 ml of combination of 2% lignocaine and 1:200000 units of adrenaline and 3 ml of 0.5% bupivacaine. 4 ml of the anesthetic mixture was injected using 23G needle at the junction of outer one-third and inner two-third of the lower orbital margin with the needle directed toward the floor of the orbit. An additional 3 ml injection was given at the supraorbital notch using a 23G needle till the hub of the needle if required. Eyelids were then closed, and intermittent pressure was applied for 5 min. For sub-Tenon's anesthesia eye was painted with 10% povidone-iodine solution and draped. Lid speculum was placed. A volume of 5 ml of anesthetic mixture was prepared with 3 ml of combination of 2% lignocaine and 1:200000 units of adrenaline and 2 ml of 0.5% bupivacaine. 0.5% of topical proparacaine was instilled. The patient was instructed to look upward and inwards. Blunt Westcott's scissors were used to make a small nick in the conjunctiva and Tenon's capsule in the inferotemporal quadrant. Sub-Tenon's cannula was then inserted to bare sclera and guided along the contour of the globe till the hub of the needle touches the sclera. 3 ml of the anesthetic mixture was slowly injected into this sub-Tenon's space. After giving the block the time of onset of akinesia was noted and graded based on complete restriction of movements in all quadrant (Grade-1), eye movements <15° in any direction of gaze (Grade 2), and eye movement >15° in any direction of gaze (Grade-3). In the presence of full eye movements, we will give 3 ml if subconjunctival injection of lignocaine.

Surgeons were asked to score peribulbar and sub-Tenon's blocks on the basis of extraocular movement, ease of the procedure.

Major and minor complications such as retrobulbar hemorrhage, globe perforation, chemosis, subconjunctival hemorrhage (SCH) were noted before starting the surgery.

The patient was asked to score the pain at the time of administration, at the end of the surgery and 1 h after surgery with the help of visual pain score analog.[3]

Statistical analysis was carried out using SPSS 19.0 software (IBM SPSS, US). For descriptive statistics percentage, mean and standard deviation were used. For inferential statistics Chi-square, independent t-test were used to find the association and difference in mean, respectively. P < 0.05 was taken as statistically significant. Time of onset shown in [Table 3] and represented in [Figure 3].

The average time of onset of akinesia with sub-Tenon's anesthesia was 2.78 ± 0.958 min and peribulbar anesthesia was 9.96 ± 2.141 min. The difference was statistically significant (P = 0.00). Extraocular movements and ease of procedure between the two groups was almost the same and not statistically significant. The incidence of minor complications such as chemosis and SCH were more in sub-Tenon's technique. Peribulbar anesthesia ranked higher on pain score (5.12 ± 1.255) at the time of administration compared to sub-Tenon's anesthesia (3.77 ± 1.716), the difference being statistically significant (P = 0.00). Pain score is shown in [Table 4] and the same is represented in [Figure 4].

Due to quick onset and fewer complications, sub-Tenon's anesthesia is slowly replacing peribulbar block in manual cataract incision surgery.[4] Our findings also support faster onset of akinesia with sub-Tenon's block (onset time 2.78 ± 0.958 min with sub-Tenon's block versus 9.96 ± 1.141 min with peribulbar anesthesia) This was supported by Azmon et al.[5] who also concluded that the time interval between the administration of anesthesia and commencement of the surgery was significantly less in sub-Tenon's block when compared to peribulbar block.

In our study, sub-Tenon's group experienced significantly less pain (3.77 ± 1.76) during the time of administration of anesthesia when compared to peribulbar (5.12 ± 1.25) (P = 0.001). Pain at the end of the surgery and 1 h postsurgery between the two groups were similar. Our observation was supported by studies done by Parkar et al.,[1] Datta et al.,[1] Samuel et al.[4] and Amzon et al.[5] who found that the sub-Tenon's anesthesia was superior to peribulbar anesthesia in controlling the pain.

The two anesthetic techniques in our study were comparable in providing globe akinesia for cataract surgery. This is in agreement with Amzon et al.[5] and Budd et al.[6] who reported that sub-Tenon's block was comparable to peribulbar block in providing adequate globe akinesia and anesthesia for cataract surgery. Some studies such as Ripart et al.[7] reported that sub-Tenon's block provided a better globe akinesia than peribulbar block during surgery. However, studies done by Samuel et al.,[4] Parkar et al.[1] showed that peribulbar anesthesia provides complete akinesia in more number of patients when compared to sub-Tenon's anesthesia; hence, peribulbar block is superior when complete akinesia is taken into consideration.

In our study, time of onset of akinesia in sub-Tenon's group was (2.78 ± 0.958 min) which was significantly less (P = 0.001) when compared to that of peribulbar anesthesia (9.96 ± 1.141 min). This was supported by Biggs et al.[8] who also concluded that the time interval between the administration of anesthesia and commencement of the surgery was significantly less in sub-Tenon's block when compared to peribulbar block.

The amount of anesthetic mixture (60% of lignocaine with adrenaline and 40% of bupivacaine) used for peribulbar anesthesia is 7 ml and for sub-Tenon's anesthesia is 3 ml. Significantly less amount of anesthetic solution is used in sub-Tenon's. This is supported by Briggs et al.[8] who also concluded that sub-Tenon's anesthesia requires lesser anesthetic solution and a shorter time interval from administration to surgery.

The incidence of minor complications such as chemosis and SCH was found to be significantly (P = 0.001) higher in the sub-Tenon's technique (n = 26, chemosis-12, SCH-10, chemosis + SCH-4) when compared to peribulbar group (n = 5 = chemosis). Budd et al.[6] also reported the same in his study. Demography of the study is shown is [Table 1] and [Table 2], which is represented in [Figure 1] and [Figure 2]. This may be due to damage of the subconjunctival vessels during dissection into the sub-Tenon's space and chemosis was probably due to the injection getting deposited into the wrong anatomical plane. These complications, however, did not lead to cancellation of any surgeries in our study. Some studies such as Samuel et al.[4] and Sarkar et al.[9] did not show any difference in the complication rates between the two groups.